Pollution factors

The consideration of a pollutant’s properties is a particularly valuable approach when examining real-life pollution effects, since such an assessment requires both the evaluation of its general properties and the local environment. This may include factors such as:

• toxicity

• persistence

• mobility

• ease of control

• bioaccumulation

• chemistry

Toxicity

Toxicity represents the potential damage to life and can be both short and long term. It is related to the concentration of pollutant and the time of exposure to it, though this relationship is not an easy one. Intrinsically highly toxic substances can kill in a short time, while less toxic ones require a longer period of exposure to do damage.

Persistence

This is the duration of effect. Environmental persistence is a particularly important factor in pollution and is often linked to mobility and bioaccumulation. Highly toxic chemicals, which are environmentally unstable and break down rapidly, are less harmful than persistent substances, even though these may be intrinsically less toxic.

Mobility

The tendency of a pollutant to disperse or dilute is a very important factor in its overall effect, since this affects concentration. Some pollutants are not readily mobile and tend to remain in ‘hot-spots’ near to their point of origin. Others spread readily and can cause widespread contamination, though often the distribution is not uniform. Whether the pollution is continuous or a single event, and if it arose from a single point or multiple sources, form important considerations.

Ease of control

Many factors contribute to the overall ease with which any given example of pollution can be controlled, including the mobility of the pollutant, the nature, extent or duration of the pollution event and local site-specific considerations. Clearly, control at source is the most effective method, since it removes the problem at its origin.

Bioaccumulation

Some pollutants, even when present in very small amounts within the environment, can be taken up by living organisms and become concentrated in their tissues over time. This tendency of some chemicals to be taken up and then concentrated by living organisms is a major consideration, since even relatively low background levels of contamination may accumulate up the food chain.

Chemistry

Pollution effects are not always entirely defined by the initial nature of the contamination, since the reaction or breakdown products of a given pollutant can sometimes be more dangerous than the original substance. This is of particular relevance, since the principle underlying much of practical bioremediation in general involves the breakdown of pollutants to form less harmful products.

This is further complicated in that while the chemistry of the pollutant itself is clearly important, other substances present and the geology of the site may also influence the outcome. Accordingly, both synergism and antagonism are possible. In the former, two or more substances occurring together produce a combined pollution outcome, which is greater than simply the sum of their individual effects; in the latter, the combined pollution outcome is smaller than the sum of each acting alone.

Biotechnology can be used to assess the well-being of ecosystems, transform pollutants into benign substances, generate biodegradable materials from renewable sources, and develop environmentally safe manufacturing and disposal processes.

Environmental biotechnology is the application of recognized biotechnology processes for the protection and restoration of the quality of the environment, especially with a long-term perspective. It takes advantage of appropriately qualified living organisms and employs genetic engineering to improve the efficiency and cost, which are key factors in the future widespread exploitation of organisms to reduce the environmental burden of toxic substances. It is not a new area of interest, because some of the issues of concern are familiar examples of “old” technologies, such as composting, wastewater treatment etc. In its early stage, environmental biotechnology has evolved from chemical engineering, but later, other disciplines (biochemistry, environmental engineering, environmental microbiology, molecular biology, ecology) also contribute to environmental biotechnology development.

Much pollutant can be readily degraded or removed thanks to biotechnological solutions (Fig. 3), which involve the action of microbes, plants, animals under certain conditions that envisage abiotic and biotic factors, leading to non-aggressive products through mineralization, transformation or immobilization.

Fig. 3. Sources of environmental pollutants and factors that influence their removal from the environment.

In view of the urgent need of an efficient environmental biotechnological process, researchers have devised a technique called bioremediation, which is an emerging approach to rehabilitating areas fouled by pollutants or otherwise damaged through ecosystem mismanagement.